This invention relates to control of an intake fresh air amount of an engine provided with a turbocharger.
Tokkai Hei 11-132049 published by the Japanese Patent Office in 1999 discloses a method of processing a command signal for enhancing the response characteristics of the supercharging pressure control of a turbocharger of an engine. The turbocharger is provided with an exhaust gas turbine driven by the exhaust gas of the engine, and a compressor which rotates together with the exhaust gas turbine to supercharge the intake air of the engine. The turbocharger is further provided with a variable nozzle that regulates the inflow cross-sectional area of exhaust gas to the exhaust gas turbine.
The inflow cross-sectional area of exhaust gas varies according to the opening of the variable nozzle that is varied by an actuator.
This prior art technique discloses an idea that the intake air amount of the engine varies with a first order delay with respect to the command signal input to the actuator, and proposes to apply an advance processing to the command signal for cancelling out the first order delay in order to enhance the precision of control of the intake air amount of the engine.
There are the following problems in taking the delay from the variation of the command signal to the actuator, until the intake air amount of an engine changes, to be a simple first order delay.
Various kinds of delay may be anticipated between the command signal input to the actuator and the variation of the intake air amount of the engine, such as a delay depending on the flow velocity of intake air and exhaust gas, a turbo lag due to the construction of the gas turbine/compressor, and a delay in the operation of the actuator itself.
These lags do not necessarily vary with the same parameters.
For example, a time constant of the lag depending on the flow velocity of the intake air and exhaust gas and a time constant of the turbo lag, vary depending on the exhaust gas amount of the engine. On the other hand, a time constant of the operating delay of the actuator is fixed regardless of the exhaust gas amount.
Therefore, it is difficult to enhance the precision of controlling the intake air amount by simply applying an advance processing based on a first order delay to the command signal to the actuator.
It is therefore an object of this invention to perform delay compensation in the control of a turbocharger with higher precision.
In order to achieve the above object, this invention provides a control device for a turbocharger of an engine, wherein the turbocharger is provided with an actuator which adjusts an intake air amount of the engine according to a command signal. The control device comprises a sensor which detects a running state of the engine, and a controller functioning to set a target intake air amount of the engine based on the running state, calculate an operational target value of the actuator based on the target intake air amount, calculate a first compensation value of a response delay from operation of the actuator to variation of the intake air amount, calculate a second compensation value of an operating delay of the actuator with respect to an input of the command signal to the actuator, calculate the command signal by performing a processing based on the first compensation value and the second compensation value on the operational target value, and output the command signal to the actuator.
This invention also provides a control method of a turbocharger of an engine, wherein the turbocharger is provided with an actuator which adjusts an intake air amount of the engine according to a command signal. The control method comprising detecting a running state of the engine, setting a target intake air amount of the engine based on the running state, calculating an operational target value of the actuator based on the target intake air amount, calculating a first compensation value of a response delay from operation of the actuator to variation of the intake air amount, calculating a second compensation value of an operating delay of the actuator with respect to an input of the command signal to the actuator, calculating the command signal by performing a processing based on the first compensation value and the second compensation value on the operational target value, and outputting the command signal to the actuator.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.